VOLUME MEASUREMENT OF SINGLE TREES

ABSTRACT

Following an earlier article, it is claimed that the height/diameter curve, in the “main stem” of all normally grown forest trees, is parabolic; so that for this length, the height/sectional area relationship is linear. Other than the variation in the height/diameter ratio of different trees, variation of “taper” results chiefly from differences of stem profile in the crown and at the butt.

The “taper line” is defined as the graphical linear relation, in the main stem, between height and sectional area. Projection of the taper line to intercept the vertical and horizontal axes at “parabolic height” and “parabolic base” respectively, gives a triangle, from which “parabolic volume,”— vp—, can be computed, from the formula: — vp = ½ height x base. The units of measurements used in this article are feet, square feet and cubic feet, for height, sectional area and volume respectively. (Metric, or other units, can course be used if desired.)

For plantation grown coniferous trees, and for “second growth” crops in general, experience suggests that parabolic volume will ordinarily be found to be a close approximation to total stem volume; and in such crops therefore, to be a universal unit for comparative purposes. (For very large, old, umbrageously crowned and irregularly shaped trees, precise estimation of volume is not possible by any practicable method. Often when it is practicable, it may not be warranted, because of hidden defects, etc.).

Other important uses of the taper line method of measurement are detailed, e.g.:-

1.	Not only can tree measurements be checked in the field at the time of making them, but checks can be made, at any time, of measurements made by persons in other parts of the world.
2.	By comparison with other methods, estimation of total stem volume; merchantable volume; volume by assortments; and value of whole trees by assortments, is more accurate and much quicker.
3.	The measurement of standing trees, which is so important in research work, is greatly facilitated.
4.	Synthesis and analysis of growth measurements are simplified.
5.	Changes, as a result of treatment, in any part of the stem profile, or in bark thickness, can be detected most reliably by the taper line method of measurement, which is therefore the best method for scientific purposes which involve tree measurement.
6.	The technique outlined for the measurement of single trees, can be generalised, so that it can be used for volume table preparation, which, however, is beyond the scope of the present article.